China has world's largest 'SeafoodPrint' China has world's largest 'SeafoodPrint'

China catches and consumes more fish than any other nation, according to findings published Wednesday in National Geographic magazine, while the United States ranks third.

The study measures what its researchers call the "SeafoodPrint" of each country, factoring in the type of fish and total haul to gauge the extent to which a nation exploits the ocean. The United States comes in as high as it does in part because Americans prefer top predators such as Atlantic salmon.

University of British Columbia Fisheries Centre professor Daniel Pauly, who conducted the study with National Geographic fellow Enric Sala, said scientists need to focus on what kind of fish are being consumed because "every fish is different."

"A pound of tuna represents roughly a hundred times the footprint of a pound of sardines," Pauly said.

"Anchovies are different from tuna in the same way that gazelles are different from lions (or rather field mice from lion-eating dragons, to account for the size difference)," Pauly wrote in an e-mail. "This should make obvious how illusory it is to think that the consumption of tuna by lots of people can ever be 'sustainable.' "

The researchers, whose project was underwritten by UBC, along with the National Geographic Society and the Pew Charitable Trusts, used a unit of measurement based on "primary production," the microscopic organisms at the bottom of the marine food web that are required to make a pound of a given type of fish.

A single thousand-pound tuna might need to eat as many as 15,000 smaller fish in a year, for example, which means eating one pound of tuna is equivalent to 100 pounds of tilapia.

"The footprint of fishing could be used as the common currency to determine what's the limit of what we can take out of the ocean," Sala wrote in an e-mail. "We could think about reducing our footprint like we're thinking of reducing carbon emissions."

Human population remains a major driver of seafood consumption: It helps account for why China - with about 1.3 billion people - ranks at the top of the list with 13.6 million metric tons of fish a year, even though it has a lower per-capita level of consumption than the United States.

The report also highlights a divide in which rich countries are increasingly buying their fish - often from poorer nations that don't consume nearly as much. Japan is second in overall fish consumption and buys more than twice as much as it catches. By contrast, Peru ranks No. 2 in terms of its annual catch, largely because its anchovies help supply fish meal for farm-raised pigs and chickens, as well as fish. Peru's citizens consume very little fish themselves.

Anchovies and other small fish represent a third of the world's total seafood catch, Pauly wrote, and would represent "our major reserve of seafood" if humans stopped raising fish-eating chickens and pigs.

Researchers argue that nations should consider forging a global treaty to set seafood-consumption targets and declare parts of the sea off-limits to fishing.